1. Department of Mechanics and Machine Design, Faculty of Mechanical Engineering, Opole University of Technology, 5 Mikołajczyka St., Opole 45-271, Poland
2. Department of Mechanics and Machine Design, Faculty of Mechanical Engineering, Opole University of Technology, 5 Mikołajczyka St., Opole 45-271, Poland (Corresponding author), e-mail: ma.kurek@po.opole.pl